Human Physiology. 235 



inconvenience, and with less feeling of chill than in an ordinary 

 English temperature. And when one is out in a temperature 

 of 40 to 60 of frost, he finds a healthy exhilaration, and a 

 pleasant glow in such an atmosphere. 



The production and maintenance of heat in the body is a 

 vital process for which chemistry does not fully account. The 

 union of carbon and hydrogen with oxygen, always going on in 

 the system, is accompanied by the evolution of heat, but it 

 cannot be shown that the heat developed in birds while hatch- 

 ing their eggs, or the external heat of fever, or that which is 

 connected with the reproductive process in certain plants is 

 the result of the destruction of tissue. The heat of inflamma- 

 tion has more resemblance to that of electricity, than that 

 produced by combustion. 



The human body, like all masses of matter, is constantly 

 sending off heat by radiation. Clothing hinders this in some 

 degree, and so aids us to husband our heat. When warmly 

 clothed we waste less matter, and need less food to supply the 

 waste. When the temperature rises above 70 Fahrenheit, 

 we need more than radiation. Then the action of the sweat- 

 forming glands is increased, and the body is cooled by evapora- 

 tion. It is this profuse perspiration, and the rapid taking up of 

 the heat of the skin by the conversion of water into vapour, 

 that enables men to live near furnaces, and even in hot ovens. 

 But these sudoriferous glands act under the influence of the 

 nerves, which are the inmost organs of life. When the living 

 power of the nerves of organic life is exhausted when life is 

 spent the temperature can no longer be maintained. The 

 extremities become cold and numbed; a clammy coldness 

 overspreads the skin ; the senses are dulled ; the brain ceases 

 to act; respiration becomes slow, slower, and stops; soon after 

 the heart ceases to beat. The eyes lose their brightness, and 

 assume a glassy stare ; the whole body becomes rigid the last, 

 action of vegetative, or the mere bodily life ; then comes relaxa- 



